1. Field of the Invention
The invention relates to adapters for sustaining multiple input/output exchange processes concurrently between plural input/output (I/O) channels and a storage access subsystem of a data processing system.
2. Prior Art
Systems and devices for sustaining multiple data communication processes concurrently, in time division multiplex mode, are generally well known. The present adapter is considered unique in respect to its specific arrangement of timeshared buffer arrays and multiplexed control sequencers for sustaining multiple storage request and response transfer activities concurrently; with a small amount of hardware, with small likelihood of interference (overrun or blocking), and with relatively small burden on (and complexity of) channel controls.
Sharing of controls for storage access by multiple input/output channels is not original as a general proposition. However, the known systems either lack ability to sustain multiple request and response activities concurrently (e.g., the 2846 channel controller feature of the IBM System/360 Model 67) or achieve such ability by providing separate buffer facilities for request and response activities.
The present adapter features time-coordinated sequencers and shared buffer arrays for processing requests and responses concurrently. It also features simple controls for checking associations of requests and responses and for timing out active requests. These ancillary functions are carried out without delaying response handling and without adding a factor of potential unreliability to the handling of requests and responses.